1. Field of the Invention
This invention relates to the field of wireless fixed subscriber units in a telecommunications system. In particular, the invention relates to assignment of fixed subscriber units to base stations.
2. Description of the Related Art
In various areas, particularly in developing countries, wired telephone service is difficult to install in residential buildings, offices and other locations. In such circumstances, telephone service can be provided by installing a radio base station in or near the telephone central office and a radio transceiver, called a fixed subscriber unit (FSU) in or near the subscriber""s premises. The radio base station is connected to the local exchange through wires or radio links. The FSU allows the subscriber equipment, such as a common telephone set, to communicate with the telecommunications network by communicating over a radio link with the base station instead of wires. Such a system may be referred to as a wireless local loop (WLL). Even in some areas in which a wired telephone network has been set up, a wireless local loop system may be employed. Details about the wireless local loop system are provided in the Te Kai Ping bulletin issue 9-322254 in Te Biao Ping bulletin issue 9-510377 which is hereby incorporated herein by reference. Telephone sets connected to an FSU can transmit and receive voice signals much like ones connected to a wired network.
Often a system includes a number of different base stations and a number of different FSUs. In various circumstances, such as when an FSU is introduced into a system or is powered on, the FSU must be assigned to a particular base station for communication with the network. In such a circumstance, the FSU must be matched with a particular base station to which it will be assigned. It would be desirable to achieve an efficient assignment of an FSU to a base station and a sufficient communication between the FSU and base station.
The embodiment of the invention is directed to a method of assigning a fixed subscriber unit (FSU) to communicate with a particular base station in a system including a plurality of wireless FSUs. Each FSU is coupled to a subscriber communication device, and each FSU is configured to communicate wirelessly with at least a base station. The system includes a plurality of base stations, which are coupled to a telecommunications network. The FSU measures signal strength of a set of base stations. The FSU sends a message with the measured signal strength of the set of base stations to a base station. Circuitry coupled to the base station determines at least a base station to which the FSU is to be assigned based on the message and additional information in the circuitry coupled to the base station. In response to the determining by the circuitry coupled to the base station, the base station sends to the FSU a message including the base station to which the FSU is to be assigned.
The additional information in the circuitry coupled to the base station may take various forms. For example the additional information may comprise measured signal strength of base stations sent by FSUs other than the FSU. The additional information in the circuitry coupled to the base station comprises usage patterns in various base stations to which the FSU could be assigned. The additional information in the circuitry may comprise information regarding availability of base stations to additional FSUs.
According to one aspect of the invention, the FSU may periodically measure signal strength of surrounding base stations. The FSU sends a message with measured signal strength to a base station, and in response to the message, the base station sends an updated list of base stations to which the FSU may be assigned.
According to one embodiment to the invention, the FSU maintains a prioritized list of base stations to which the FSU may be assigned. The prioritized list may first be based on measured signal strength of the base stations and then updated in response to a message from the base station. The message from the base station may include a new prioritized list of base stations and the FSU may replace the prioritized list of base stations with the new prioritized list of base stations from the base station. The FSU may attempt to achieve an assignment with the highest prioritized base station on the list, and, if the FSU is not able to achieve the assignment with the highest prioritized base station, the FSU may achieve an assignment with another base station and later attempt to achieve an assignment with the highest prioritized base station.
Another embodiment to the invention is directed to a communications system. The communication system includes a plurality of base stations that are coupled to a telecommunications network. The communication system includes a plurality of subscriber communication devices. The communication system includes a plurality of fixed wireless subscriber units (FSUs). Each subscriber communication device is coupled to an FSU. Each FSU is configured to communicate wirelessly with at least a base station. Each FSU includes circuitry that measures signal strength of a set of base stations and sends a message with the measured signal strength of the set of base stations to a base station. The communication system includes circuitry coupled to the base stations that determines at least a base station to which an FSU is to be assigned based on the message and additional information in the circuitry coupled to the base station. The circuitry causes, in response to the determining, the base station to send to the FSU a message including the base station to which the FSU is to be assigned.
Another embodiment of the invention is directed to an apparatus for use in a telecommunications system. The apparatus has circuitry that determines at least a base station to which a wireless FSU is to be assigned in response to (a) a message from the FSU including measured signal strength of a set of base stations and (b) additional information. The measured signal strength is measured by the FSU. The circuitry also causes a base station communicating with the FSU to send a message including the base stations to which the FSU is to be assigned.
Another embodiment to the invention is directed to a wireless FSU. The FSU includes an interface to a subscriber communication device and a wireless base station interface. The FSU also includes circuitry that measures signal strength of a set of base stations and sends a message with the measured signal strength of the set of base stations to a base station. The circuitry also receives a message from the base station including a base station to which the FSU is to be assigned based on the message sent to the base station and based on additional information. The circuitry attempts to achieve an assignment to the base station sent in the message from the base station.